Transcript C11- DNA and Genes

C11- DNA and Genes
Chapter 11
Contents
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11-1 DNA: The Molecule of Heredity
11-2 From DNA to Protein
Protein Synthesis video
11-3 Genetic Changes
11-1 DNA: The Molecule of Heredity
• Genetic info in DNA controls organism’s traits
11-1 DNA: The Molecule of Heredity
• Genetic info in DNA controls organism’s traits
• Determines structure of proteins built
11-1 DNA: The Molecule of Heredity
• Genetic info in DNA controls organism’s traits
• Determines structure of proteins built
• Hershey & Chase (1952) used radioactively tagged
viruses to infect bacteria and proved DNA is genetic
material
11-1 DNA: The Molecule of Heredity
• Genetic info in DNA controls organism’s traits
• Determines structure of proteins built
• Hershey & Chase (1952) used radioactively tagged viruses
to infect bacteria and proved DNA is genetic material
Nucleotide Structure
• DNA polymer of repeating
units called nucleotides.
Nucleotide Structure
• DNA polymer of repeating
units called nucleotides.
• 3 parts
– Simple sugar
– Phosphate
• Phosphorus w/ 4 O
– Nitrogenous base
Nucleotide Structure
• DNA polymer of repeating
units called nucleotides.
• 3 parts
– Simple sugar
– Phosphate
• Phosphorus w/ 4 O
– Nitrogenous base
• C ring w/ 1 or more
N & a base
– Adenine (A)
– Cytosine (C)
– Guanine (G)
– Thymine (T)
Nucleotides
• Join in long chains
• with phosphates
connecting
• to sugar of next unit
• to form a backbone
Nucleotides
• Join in long chains
• with phosphates
connecting
• to sugar of next unit
• to form a backbone
• with the bases sticking
out like the teeth of a
zipper.
• Adenine = Thymine
• Guanine = Cytosine
Structure of DNA
• James Watson & Francis
Crick (1953) unraveled the
structure of DNA.
• Double Helix structure
Nucleotide Sequence
• Forms unique genetic
information of
organism
Nucleotide Sequence
• Forms unique genetic
information of
organism
• Can be used to
determine evolutionary
relationships between
organisms
Nucleotide Sequence
• Forms unique genetic
information of
organism
• Can be used to
determine evolutionary
relationships between
organisms
• Or familial relationships
• DNA can identify
victims or criminals
Replication of DNA
• Copies DNA in chromosome during interphase
Replication of DNA
• Copies DNA in chromosome during interphase
• Enzyme breaks the hydrogen bond between bases
Replication of DNA
• Copies DNA in chromosome during interphase
• Enzyme breaks the hydrogen bond between bases
• Complimentary base pairing allows duplication
Replication of DNA
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Copies DNA in chromosome during interphase
Enzyme breaks the hydrogen bond between bases
Complimentary base pairing allows duplication
Each strand is a template
11-2 From DNA to Protein
• DNA controls the
production of proteins.
• Proteins are key cell
structures & regulators of
cell functions.
11-2 From DNA to Protein
• DNA controls the
production of proteins.
• Proteins are key cell
structures & regulators of
cell functions.
• RNA, another nucleic acid
carries out DNA’s
instructions
11-2 From DNA to Protein
• DNA controls the
production of proteins.
• Proteins are key cell
structures & regulators of
cell functions.
• RNA, another nucleic acid
carries out DNA’s
instructions
• Structure differs 3 ways
– Single-stranded
– Sugar is ribose
– Uracil replaces thymine
Three Types of RNA
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Protein assembly line:
Messenger RNA (m-RNA)
Ribosomal RNA (r-RNA)
Transfer-RNA (t-RNA)
Three Types of RNA
• Protein assembly line:
• Messenger RNA (m-RNA)
– Brings instructions from
DNA to ribosome in the
cytoplasm
• Ribosomal RNA (r-RNA)
• Transfer-RNA (t-RNA)
Three Types of RNA
• Protein assembly line:
• Messenger RNA (m-RNA)
– Brings instructions from
DNA to ribosome in the
cytoplasm
• Ribosomal RNA (r-RNA)
– Reads instructions to
assemble protein by
binding to m-RNA
• Transfer-RNA (t-RNA)
Three Types of RNA
• Protein assembly line:
• Messenger RNA (m-RNA)
– Brings instructions from
DNA to ribosome in the
cytoplasm
• Ribosomal RNA (r-RNA)
– Reads instructions to
assemble protein by
binding to m-RNA
• Transfer-RNA (t-RNA)
– Delivers amino acids for
assembly to ribosome
Transcription
• Occurs in the nucleus by
enzymes copying part of
the DNA
– Enzyme unzips DNA
– Assembles singlestrand copy
Transcription
• Occurs in the nucleus by
enzymes copying part of
the DNA
– Enzyme unzips DNA
– Assembles singlestrand copy
– DNA rezips after mRNA detaches
Transcription
• Occurs in the nucleus by
enzymes copying part of
the DNA
– Enzyme unzips DNA
– Assembles singlestrand copy
– DNA rezips after mRNA detaches
– m-RNA leaves nucleus
by nuclear pore to enter
cytoplasm
Transcription
• Occurs in the nucleus by
enzymes copying part of
the DNA
– Enzyme unzips DNA
– Assembles singlestrand copy
– DNA rezips after mRNA detaches
– m-RNA leaves nucleus
by nuclear pore to enter
cytoplasm
– Carries instructions to
ribosome
Translation
• Occurs in the ribosome
• Process of converting
series of bases into chain
of amino acids forming a
protein
Translation
• Occurs in the ribosome
• Process of converting
series of bases into chain
of amino acids forming a
protein
– r-RNA reads sequence
of 3 bases (codon)
Translation
• Occurs in the ribosome
• Process of converting
series of bases into chain
of amino acids forming a
protein
– r-RNA reads sequence
of 3 bases (codon)
– t-RNA anticodon
matches up with the
codon from m-RNA and
supplies the amino acid
needed
Translation
• Occurs in the ribosome
• Process of converting
series of bases into chain
of amino acids forming a
protein
– r-RNA reads sequence
of 3 bases (codon)
– t-RNA anticodon
matches up with the
codon from m-RNA and
supplies the amino acid
needed
– Ribosome translates the
next codon until finished
assembling the protein
RNA & Protein Synthesis
RNA Processing
• Introns- noncoding nucleotide sequences
• Exons- expressed sections of nucleotides
• Enzymes cut out the introns & paste the exons
together
Genetic Code
• Amino acids are the
building blocks of proteins.
• A sequence of 3
nucleotide bases code for
each of the 20 amino
acids.
• 64 different codons in mRNA
• AUG start codon
• UAA stop codon
• All organisms use the
same genetic code.
Translating the m-RNA Code
• T-RNA leaves amino acid
in position to form peptide
bond with previous amino
acid
Translating the m-RNA Code
• T-RNA leaves amino acid
in position to form peptide
bond with previous amino
acid
• The ribosome continues to
assemble amino acids
until stop codon is
reached.
Translating the m-RNA Code
• T-RNA leaves amino acid
in position to form peptide
bond with previous amino
acid
• The ribosome continues to
assemble amino acids
until stop codon is
reached.
• Translation is complete
Translating the m-RNA Code
• T-RNA leaves amino acid
in position to form peptide
bond with previous amino
acid
• The ribosome continues to
assemble amino acids
until stop codon is
reached.
• Translation is complete
• Amino acid chain is
released & twists into
complex folded shape of
protein
Translating the m-RNA Code
• T-RNA leaves amino acid
in position to form peptide
bond with previous amino
acid
• The ribosome continues to
assemble amino acids
until stop codon is
reached.
• Translation is complete
• Amino acid chain is
released & twists into
complex folded shape of
protein
• Become enzymes &
structures
11-3 Genetic Changes
• Mutation- any change in
DNA sequence
• Caused by errors in
– Replication
– Translation
– Cell division
– Or by external agents
such as UV or chemical
exposure
Mutations in Reproductive Cells
• Changes in the sequence
of nucleotides can cause:
– Altered gene in offspring
– New traits
– Nonfunctional protein
with structural or
functional problems in
cells
– Embryo may not survive
– Positive effect
Mutations in Body Cells
• Does not pass on to
offspring
• May cause problems for
the individual
• Impair function of the cell
• Contributes to aging
• Can cause cancer by
making cells reproduce
rapidly
Effects of Point Mutations
• Point mutation - Change
in a single base pair in
DNA
• Can change entire
structure of the protein
• Error may or may not
affect protein function
• Ex. Sickle cell anemia
Frameshift Mutations
• A single base is added to
or deleted from DNA
• Shifts the reading of the
codons by one base
• Nearly every amino acid
after the insertion or
deletion will be changed
Chromosomal Alterations
• Chromosomal mutations
• Deletions -Parts break &
are lost during mitosis or
meiosis
• Insertions- Parts rejoin
incorrectly
• Inversions- Rejoin
backwards
• Translocations- Join
other chromosomes
• Common in plants
Causes of Mutations
• Mutagens- agents that
cause change in DNA
– Radiation
• X-rays
• Gamma rays
• Ultraviolet light
• Nuclear radiation
– Chemicals
• Dioxins
• Asbestos
• Benzene
• Formaldehyde
– High temperatures
6-legged frog
aflatoxin
Repairing DNA
• Repair mechanisms have
evolved:
• Enzymes proofread DNA
& replace incorrect
nucleotides.
• The greater the exposure
to the mutation, the less
likely it can be corrected.
• Limit exposure to
mutagens.